MINOR: Annotate KafkaAdminClientTest.testAlterClientQuotas() with @Test

KafkaAdminClientTest.testAlterClientQuotas() is uncalled. It is clearly intended to be a test method, but lacks `Test`.

Author: Tom Bentley <tbentley@redhat.com>

Reviewers: Gwen Shapira, Brian Byrne

Closes #8456 from tombentley/MINOR-annotate-test-method

clients/src/test/java/org/apache/kafka/clients/admin/KafkaAdminClientTest.java

@@ -3355,6 +3355,7 @@ public class KafkaAdminClientTest {
             ClientQuotaFilterComponent.ofEntityType(ClientQuotaEntity.USER));
     }
 
+    @Test
     public void testAlterClientQuotas() throws Exception {
         try (AdminClientUnitTestEnv env = mockClientEnv()) {
             env.kafkaClient().setNodeApiVersions(NodeApiVersions.create());